Is the URL you show working when added as a hyperlink to a topic? MindManager has been known to truncate at the "?".

I don't think you will be able to modify the action of clicking the hyperlink icon to add e.g. a tag value to the hyperlink before perfroming the action.

A macro could be written to copy the tag value to the end of the hyperlink.

You would populate the map and then run the macro to set all the hyperlinks.

BUT back to basics and hoping I ma not teaching you to suck eggs! Why not just drag and drop the URLs from the SharePoint web page to the map? You drag any linked items on a SharePoint page to a map. And you will get their descriptive text on the map as a bonus.